Advances in technology have enabled high speed wireless communication and spurred the growth of wireless, and now mobile computing systems. This technology has enabled many new wireless services and systems including wireless LANs. Wireless LANs are the first step toward a mobile computing environment.
Several systems for mobile and wireless computing have been disclosed. Xerox's tab system uses a small hand-held device, called a tab, as a terminal which then interacts with a surrounding network which contain the intelligence. This allows the users to pick up and use an arbitrary tab and immediately have access to their environment. The tab system has an infra-red link for transmitting and receiving data which allows communication in office size cells that are connected to an installed backbone network.
The Infopad system uses an approach similar to a terminal device, and is connected by a high speed RF modem for access of interactive data. The Infopad relies on the surrounding network to provide the intelligent resources, while acting as a terminal for the data.
An intermediate approach splits the intelligence between the device and the network. Some of the computation can be carried out using powerful processing resources in the backbone network instead of on the mobile system which has limited processing resources as well as a limited power budget. Applications typically utilize as much communications bandwidth as is available by adaptively altering the amount of processing on the backbone network verses at the mobile system.
A third approach places the intelligence in the mobile system and utilizes the backbone network to access other devices on a peer to peer basis. This approach is similar to the current model of networked computing, and is supported by wireless LAN systems running Mobile IP. Mobile IP allows the definition of a mobile subnetwork having many mobile systems associated with it. When communicating with a mobile system, data is first sent to any one of several fixed hosts associated with that subnetwork. The fixed hosts either know where the mobile system is, which base station the mobile system is communicating with, or can determine this by quering a set of other base stations.
The WaveLAN system is a wireless LAN system that allows wireless extension of existing Ethernet networks. The WaveLAN has been used as the physical layer for several mobile computing systems.
Wireless untethered computing allows continual connection of mobile systems to the network backbone as users move around their office, corridors and conference rooms. The system should support several models of access, from terminals to intelligent mobile hosts. In order to support this model, mobile systems must be equipped with suitable wireless interfaces, wireless base stations must be installed and the backbone network must be enhanced to support mobile users. Existing wireless designs were unsuitable to allow flexible and innovative handoff and MAC schemes.
Although considerable progress has been made with the use of wireless technology and broadband networks, many technical problems remained to be solved before a vision of omnipresent tetherless access to multimedia information can be realized. Accordingly, there is a need to provide a flexible hardware architecture which is reconfigurable for different protocols and different radio modem control.